The present invention relates to dry type patches for teeth whitening which can be attached to the teeth without using a tray, have a contact area shape capable of minimizing irritation to gums, and have a natural feeling to wearers. Since the patches for teeth whitening strongly adhere to the teeth, they do not disturb the wearer's daily life and are not easily detached from the teeth during the wearer's mouth movements, such as for example, coughing and/or talking in a loud voice.
As people's interest in whitening their teeth increases, a number of tray products providing teeth whitening effects in a short period of time have become commercially available. These tray products are largely divided into over-the-counter products (“OTC products”) and products requiring dentist's prescriptions. The OTC products are available in the market at low cost, but are known to have many problems. For example, since the OTC products use one-sized and single-shaped trays, they do not fit various sizes and shapes of users' teeth, which causes irritation to the teeth due to poorly fitting trays and gels excessively applied onto the trays. In addition, since the leakage of gel may take place in use, there are problems in terms of convenience and safety. Further, since most of the OTC products are highly noticeable, it is difficult to use them in daily life. Accordingly, the OTC products are limited in their use, for example, for overnight use only. On the other hand, since the products requiring dentist's prescriptions are precisely manufactured according to the contour and size of patient's teeth, the problems of the OTC products can be solved to some extent but are disadvantageous in that they are expensive and a patient needs to regularly see a dentist.
To overcome the above problems of the gel-filled tray products, strips for teeth whitening without the use of trays have been developed and a number of patent applications related thereto have been filed. For instance, U.S. Pat. No. 5,310,563 (“Curtis et al.”) suggested a strip for teeth whitening which comprises a capsule obtained by encapsulating a peroxide or various ingredients in a putty-like material using a silicon polymer. The adhesion of the strip for teeth whitening to the teeth results from the elasticity of the putty such as rubber. However, meaningful attention is not given to the shape of the strip. The strip has a drawback that since the peroxide is encapsulated in the putty-like material, the whitening effects are relatively poor although the strip is attached to the teeth for the same time period. Further, since the adhesion between the strip and the teeth depends on the elastic strength, some stimuli to the teeth, such as coughing or collision with something, in a mouth in which a tongue actively moves may separate the strip from the teeth and thus the strip is returned to its initial shape.
On the other hand, 3M developed a strip for teeth whitening using only a gel retention insert without the use of a tray. The gel retention insert is a product that was developed in order to further enhance the adhesion between gel and the teeth, and has a microstructure. The gel retention insert used as the strip for teeth whitening has a microstructure in which a PSA (pressure sensitive adhesive) is used and teeth whitening ingredients are dispersed. However, the teeth whitening effects of the gel retention insert are not verified, like trays manufactured using a gel retention insert having a water-insoluble microstructure. Since most polymers used as PSAs employ solvents unsuitable for oral products, e.g., methylene chloride or ethylacetate, etc, instead of water or alcohol, they are considered to be unsuitable to directly attach to the teeth in the oral cavity. In addition, in the case that an acrylic polymer (a wet PSA) having a low compatibility with a peroxide is used as a strip for teeth whitening, the strip for teeth whitening is thought to be inappropriate for commercialization.
U.S. Pat. No. 6,419,906, issued to Colgate, discloses a strip for teeth whitening comprising a thermoplastic ethyleneoxide polymer and a solid percarbonate as a teeth whitening agent. However, since the ethyleneoxide polymer is highly compatible with the peroxide but has a low adhesion to the teeth, it is believed that the wearability of the strip is poor.
In particular, such strips for teeth whitening were commercialized by P&G. Since the strip for teeth whitening is manufactured by uniformly and thinly applying teeth whitening ingredients onto a thin and flexible polyethylene strip without the use of a tray, problems of conventional tray products can be solved. Since the strip for teeth whitening is a wet type, the adhesive strength of the strip to the teeth is not so strong. Accordingly, the strip can be easily attached and peeled off, but has a drawback in that when coughing and laughing out loud, it is not attached at a desired position for a desired period of time and can be easily detached from teeth, in particular, from lower teeth in comparison to upper teeth. As a patented product associated with these strip products, a strip with rounded corners is disclosed in U.S. Pat. No. 5,879,691. Thereafter, based on the finding that a particular shape a strip for teeth whitening is essential to attach a teeth whitening agent to a desired site for a desired time, P&G developed a strip having various shape and filed PCT publication WO 2001-014736. The strip for teeth whitening has a shape in which the outer surface of 4 front teeth and 2 canine teeth is covered while allowing the tips of the two canine teeth to be uncovered. That is, the strip is of a shape that the tips of the canine teeth are uncovered. Possible examples of the strip shape include trapezoids with or without at least one stepped side or notch and quadrangles with at least one stepped side, notch or recess. These shapes allow the strip and teeth whitening materials to adhere well to the teeth, and maintain the state without sliding from the wearer's teeth for a long period of time. As can be seen from commercialized strip products for teeth whitening manufactured by P&G, the strip products are applied to lower teeth having a relatively large size and less curved rather than upper teeth. FIGS. 1a and 1b are plan views of a strip for upper teeth and a strip for lower teeth of Crest Whitestrip (P&G), respectively.
However, although the strip for teeth whitening manufactured by P&G has a trapezoidal shape such that the tips of 2 canine teeth are not covered with the strip, the adhesion of the strip to the teeth is poor because the strip is a wet type. Accordingly, there is a need to improve the problem of poor adhesion.
The primary benefit of a dry type patch for teeth whitening, which was filed by the present inventors, is that when a user peels off the patch from a release liner using the hands and attaches the patch to the teeth, adhesive ingredients contained in an adhesive layer are not deposited on the hands and unwanted sites, e.g., the face and lips, due to user's error. In addition, since the patch is a dry type, it solves safety problems caused by a high concentration hydroxide used as a teeth whitening agent. That is, after the dry type patch is attached to the teeth, a glassy polymer provides strong adhesion to the teeth while being hydrated by moisture on the tooth surface and a whitening agent begins to be released. Accordingly, the dry type patch is a safe formulation having no problem in use.
However, despite these advantages of the dry type patch for teeth whitening discussed above and excellent adhesion to the teeth, when the patch comes into contact with gums containing a higher level of moisture than the teeth, the strong adhesive strength induced during hydration may cause irritation to gums.